1. Field of the Invention
This invention relates generally to a high frequency strip-line circuit and, more particularly, to a microstrip circuit for processing a microwave signal.
2. Description of the Prior Art
Transmitting and receiving information signals via satellite generally involves high-frequency signals in the microwave region of the frequency spectrum. As satellite broadcasting becomes more and more prevalent, and it becomes more accessible to the home-owner or individual end-user, it also becomes necessary to produce microwave circuitry for processing the microwave signals received from the satellite, both economically and in substantial quantities. Such microwave circuitry typically employs what are known as microstrip circuits, which form a basic building block for hybrid microwave circuits.
For example, high-frequency amplifiers are typically employed to process the received microwave signals, and circuits must be provided to match the input and output impedances of the semiconductor used as the amplifying element in such high-frequency amplifier. By providing such impedance match, the overall circuit characteristics, such as the noise factor (NF), are improved. Additionally, microstrip circuits are also typically used to provide impedance matched interconnections between various passive components, including resonators and filters, and are used as integral parts of phase shifters, oscillators, and circulators.
One known microstrip circuit, in which the input and output impedances are controlled by adjusting the dimensions of the microstrip circuit, includes a field effect transistor employed as a high-frequency amplifier in a converter for converting super high-frequency (SHF) signals to ultra high-frequency (UHF) signals. As is known, a microstrip is typically formed as a planar structure having a dielectric substrate and conducting strips forming the conductor pattern on one side of the substrate with a conducting ground plane on the other side of the substrate. In order to control the impedances of the micro-strip circuit, it is known to alter the physical dimensions of the conducting strip and, in that regard, one prior practice involves the use of depositing a plurality of small conducting elements appearing substantially as a pattern of dots in the vicinity of various tuning stubs of the microstrip circuit, and then connecting together various ones of the dots in the pattern and to the stub by hand soldering to custom match the impedances of the circuit.
In view of the increasing demand for microstrip circuits and the requirement to mass produce same with a relatively low per-unit cost, the technique of individually adjusting the impedance, as explained above, is not suitable.